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Monitoring Patients with Heart Failure

Heart & Vascular Institute Physician eNewsletter - Spring 2011

Remote monitoring is not a new concept. For years physicians have used external devices like home blood pressure monitors to online health records and internal devices that are implanted to collect physiological data. The use of these devices has increased dramatically in recent years as technology evolves, particularly in the implanted device arena.

"Over the last decade, there has been an explosion of the use of implanted defibrillator or pacemaker devices due to their effectiveness in averting sudden death or improve clinical outcomes, particularly in patients with moderate or severe heart failure," says W.H. Wilson Tang, MD, FACC, FAHA, Associate Professor of Medicine at Cleveland Clinic Lerner College of Medicine and director of the Cardiomyopathy Program. "In the past, maybe a small proportion of patients will have an implanted device. Now, it's the standard of care for a lot of patients."

Modern cardiac implanted devices monitor physiological data so electrophysiologists can determine whether the device is at optimum performance. Monitoring has focused on ensuring the functionality of the device itself. "With patients in the moderate to high-risk population connected to these implanted devices, there is a great opportunity to take a more proactive approach by getting access to such information and understanding how the patient is doing," Dr. Tang says.

There are detectable physiological signals that can serve as warning signs, if monitored. "By spotting potential changes that signal warning signs of clinical deterioration, we may identify those people earlier and find ways to help them earlier," Dr. Tang describes.

Some of the device data, such as onset of rhythm abnormalities, have been widely accepted as potentially useful information for everyday patient management. Others may be less accepted, even though they may already be available as part of the device diagnostic information. For example, a refined technique to measure impedance —the measure of how the body tissue resists electrical current flow available in some devices — may enable physicians to assess the onset and progression of congestion. Originally developed a few decades ago to monitor cardiac physiology of astronauts, the presence of higher tissue fluid content can lead to a lower impedance measure even weeks before overt congestion ensues. Measuring impedance is a crude but attractive way to identify subclinical vulnerabilities that can lead to a change in clinical status in patients with heart failure and to prevent patient admission and readmission into hospitals.

However, the variability of impedance signals calls for more in-depth study through randomized, controlled trials. Dr. Tang is currently leading one of the largest multi-center national studies to better understand how healthcare providers interpret device information, how frequently such information should be obtained remotely, and what impact they have on patient management.

"We are in a revolution where we have physiological data from a large number of patients that are readily available at the patient level and at the practice level," Dr. Tang says. "However, it is not enough to implant devices and collect data. The biggest challenge is figuring out how to use this data effectively while working efficiently and safely to improve their overall status, and we need to continue our research efforts to advance our understanding."

Another major development in this arena has been the advances in implanted devices that are specifically designed to directly monitor pressure data inside the patients' failing hearts. Several novel devices are currently in the late stages of clinical development, and the results are very promising and may even be available for clinical use in a year or two. There is even potential for patients to monitor data and manage their conditions themselves, much like how patients with diabetes mellitus control their blood sugar levels.

Other external devices also measure physiologic data. Dr. Tang says we have learned a lot already—the more we monitor, the more we know about patients. "By better understanding an individual patient's physiologic state in real time, we can personalize their treatment with fine-tuning of their medications and identify their vulnerabilities," Dr. Tang notes.

Monitoring will take more effort on the part of hospitals and healthcare providers—data collection and managing information, alone, is a significant charge from changing how we delivery our care. "It is a lot more effort for us, but is a whole new way of approaching heart failure" Dr. Tang says.

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